The sleep hormone melatonin is essential for regulating the circadian rhythm and making sure you fall asleep. Read about the latest research and its potential benefits for sleep disorders and disturbances here.

What is Melatonin?

Melatonin is derived from the amino acid tryptophan and the neurotransmitter serotonin [1].

Melatonin has many important functions in the body, including:

• Influences the circadian rhythm
• Aids the immune system
• Helps eye function
• Reduces oxidative stress
• Promotes sleep
• Controls many cellular events, including synthesis of important molecules
• Protects against radiation

The pineal gland, which is nestled in the brain, makes melatonin. The quantity of melatonin in the blood depends on the time of the day. At night there is 10 to 15 times more melatonin in the blood there is in the day, which helps people sleep [2].

Melatonin is also made by many other organs in the body, especially in the stomach [3].

If sleep is interrupted by blue light exposure at night, melatonin levels decrease drastically. In addition, melatonin levels also decrease with age [4]. However, darkness does not stimulate melatonin production. It simply permits melatonin production [5].

Melatonin Receptors

Melatonin acts by interacting with two receptor proteins, MT1 and MT2 [6].

MT1 and MT2 receptors control different stages of sleep: MT1 controls deep sleep or REM sleep, and MT2 controls the stages of sleep preceding dreaming [6].

These receptors are present in a variety of organs and immune cells, suggesting that melatonin also controls the function of the immune system and other systems throughout the body [7].

Sleep and Circadian Rhythm

The circadian rhythm is like the body’s clock. It is a built-in function that controls biological processes in a roughly 24-hour cycle [8].

A central clock is located in the SCN of the anterior hypothalamus in the brain. It controls the body’s circadian rhythm. The circadian rhythm helps control the sleep-wake cycle, body temperature, and hormone production [8].

Light from the environment influences the signals sent from the SCN [8].

Under the control of the circadian rhythm, the pineal gland produces and secretes melatonin. Under normal conditions, melatonin is secreted during the night. During daylight, there are undetectable amounts in the blood [8].

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